Method for setting up connections with guaranteed quality of service for a communications network having a resource manager

ABSTRACT

Transmission resources of one or more individual transmission links, especially of individual transmission bottlenecks, are managed by a resource manager. In the course of a setting up of a connection, the resource manager determines, by using an item of connection information, the origin and destination of the connection to be set up, and identifies whether this connection is routed over a particular transmission link. Based on the result of the determination, a message is subsequently generated and transmitted to the origin of the connection. A selection of transmission resources to be used for the connection is then carried out based on the transmitted message.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to PCTApplication No. PCT/DE01/03463 filed on 7 Sep. 2001 and GermanApplication No. 100 46 583.8 filed on 20 Sep. 2000, the contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

In many packet-oriented communications networks, such as the Internet,no Quality of Service is guaranteed for connections between terminals inthese communications networks unless additional arrangements are made.The Quality of Service (QoS) of a connection may include differenttransmission and connection resources, such as the transmissionbandwidth, transmission rate, permissible error rate and/or transmissionduration.

In modern communication systems, which are frequently based onpacket-oriented communications networks of this kind, so-called resourcemanagers are provided to ensure a specified Quality of Service. Theseare in each case assigned to a communications network or subnetwork andadminister its relevant transmission resources. With a resource manager,pre-definable transmission resources can be reserved for each specificconnection to be set up. When transmission resources have beensuccessfully reserved, the resource manager monitors the continuousavailability of the reserved transmission resources for the relevantconnection.

In many cases, connections must be established between differentsubnetworks of a communication system, the subnetworks themselves havinga very high transmission bandwidth, but being interconnected by one ormore individual transmission links with relatively low transmissionbandwidth. A typical example of this is Local Area Networks (LANs) whichare interconnected via a public telephone network. The telephone networkwith its relatively low transmission bandwidth in this case constitutesa bottleneck for data interchange between the LANs.

The problem often arises that the transmission resources of such abottleneck are usually exhausted by even a relatively small number ofconnections having a resource requirement that is typical of asubnetwork with high transmission bandwidth. This generally results in arelatively high rejection rate for connections to be routed via thebottleneck.

SUMMARY OF THE INVENTION

A potential object of the present invention is to specify a method ofsetting up connections with guaranteed Quality of Service for apacket-oriented communications network, permitting efficient monitoringof transmission resources of individual transmission links, specificallyof individual transmission bottlenecks, and allowing the rejection rateof connections to be routed via such transmission links to be reduced.

With the method according to one aspect of the invention, transmissionresources of a transmission link are administered by a resource manager.As part of connection setup, the resource manager determines, on thebasis of connection information identifying the origin and destinationof the connection to be set up, whether the connection is routed via thetransmission link. Depending on the result of this determination, amessage is then generated and transmitted to the origin of theconnection. The result of the determination can be reflected both in thecontent of the message and in the message being generated at all. At theorigin of the connection, information is therefore available which isdependent on whether the connection to be set up is routed via thetransmission link in question. Depending on the message transmitted, aselection of transmission resources required for the connection is theninitiated at the origin of the connection.

In this way, the resource requirement of a connection to be set up canbe matched to the transmission conditions of the transmission linkdepending on whether that connection is routed via the transmissionlink. This means that the rejection rate of connections to be routed viathe transmission link can be considerably reduced by, for example, firstattempting to reduce the resource requirement of the connection to apermissible level instead of immediately rejecting a connection whoseoriginal resource requirement is not available. In this case, definitiverejection of the connection only takes place if no such reduction ispossible. This enables the transmission resources of the transmissionlink to be much better utilized.

In the context of the method, the term “connection” may also be taken tomean so-called virtual connections, trunk groups, connection paths ordata streams generally, with defined origin and destination in eachcase. Origin and destination refer here, for example, to terminals,network nodes, switching equipment, communications networks, subnets andsubnetworks.

The connection Quality of Service administered by the resource managercan relate to quite different transmission resources, such astransmission bandwidth, transmission rate, permissible error rate,transmission delay and/or any other so-called QoS parameters, possiblyservice- and/or priority-class-specific.

According to an advantageous embodiment, the message can be generated asa function of the level of transmission resources of the transmissionlink, both the message content and transmission of the message dependingon the level of the resources.

According to an initial variant of the method, the message can begenerated as a function of the currently available level of resources ofthe transmission link, i.e. depending on its current load situation.This variant is particularly advantageous for transmission linksutilized by only a small number of users and having a variablebandwidth.

According to a second variant of the method, only the total availablelevel of resources of the transmission link is taken into account whengenerating the message. In this variant, the message can be used e.g. toreduce the transmission resources to be utilized for all the connectionsto be routed via the transmission link, irrespective of temporary loadfluctuations on the transmission link. In this way the number ofconnections to be set up simultaneously over the transmission link canbe increased.

According to an advantageous development, one or more existingconnections routed via the transmission link can be assigned modifiedtransmission resources depending on whether a new connection to be setup is routed via the transmission link. Transmission resources of anexisting connection can thus be reduced so that a new connection to beset up, which would otherwise be rejected, can be permitted.

In addition, using the connection information, a resource request forthe connection to be set up can be communicated to the resource managerand taken into account when generating the message. Preferably theresource request can be compared with the available level of resourcesof the transmission link by the resource manager and the message can begenerated depending on the result of the comparison. For example, thetransmission resources of the connection to be set up and/or of anexisting connection can be reduced by a corresponding message if theresource requirement exceeds the available level of resources of thetransmission link. In addition, the transmission resources of theconnection to be set up and/or of an already existing connection canalso be reduced when, after the connection has been set up in accordancewith the resource request, this leaves the transmission link withinsufficient residual transmission resources. In general, modificationof the transmission resources of the connection to be set up and/or ofan already existing connection can take place depending on the residualtransmission resources remaining for the transmission link.

According to another advantageous development, the message can includeresource information dependent on the available level of resources ofthe transmission link which is taken into account for selecting thetransmission resources to be taken up by the connection. The resourceinformation can specify, for example, the currently available level ofresources of the transmission link, a specification or allocation oftransmission resources to be taken up by the connection and/or themaximum available transmission resources available for the connection tobe set up.

The message can additionally include method information concerning thetransmission method to be used for the connection. Method information ofthis kind can be, for example, a data compression method, encodingmethod and/or a data compression stage.

According to an advantageous development, it is possible to ascertain,e.g. by the resource manager or a so-called gatekeeper, whether and/orto what extent selection of transmission resources required by theconnection is supported at the origin of the connection. The subsequentconnection setup and/or generation of the message can then take placeaccordingly.

In addition, link information can be transmitted to the resource managerallowing it to identify the transmission link. This communication oflink information also enables the resource manager to separatelyadminister a plurality of transmission links identifiable in each caseon the basis of the link information using the method.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention willbecome more apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

The FIGURE shows a schematic view of a communication system having twosubnetworks connected via a transmission link.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

The FIGURE schematically illustrates a communication system having twopacket-oriented, preferably Internet-protocol-based communicationsubnetworks LAN1 and LAN2 implemented in this embodiment as Local AreaNetworks (LANs). The Local Area Network LAN1 has a router R1 which isconnected via a transmission link US to a router R2 of the Local AreaNetwork LAN2. In the embodiment it will be assumed that the transmissionlink US has much fewer transmission resources than the Local AreaNetworks LAN1 and LAN2 and therefore constitutes a bottleneck for datainterchange between the Local Area Networks LAN1 and LAN2. A situationof this kind frequently arises in practice when, for example, severalcorporate Local Area Networks situated at different locations areinterconnected as transmission links via a public communications networkor the Internet. Local Area Networks interconnected in this way areoften also known as “Virtual Private Networks” (VPNs).

To administer transmission resources of the Local Area Networks LAN1 andLAN2 and in particular of the transmission link US, a central resourcemanager RM is disposed in the communication system. The resource managerRM has responsibility in the communication system for reservingtransmission resources for connections to be set up and for ensuring theQuality of Service of established connections. The transmissionresources or Quality of Service may relate to quite differenttransmission parameters, such as maximum or average transmissionbandwidth, transmission delay and/or transmission error rate. For allconnections requiring a Quality of Service guarantee in thecommunication system, the corresponding transmission resources must berequested from the resource manager RM and released again by theresource manager RM when the connection has been cleared down. Asalready mentioned above, the available transmission resources of thetransmission link US are much fewer than the transmission resources ofthe Local Area Networks LAN1 and LAN2. For this reason, it is theavailable level of resources of the transmission link US that is thecritical factor for monitoring the transmission resources forconnections routed via the transmission link US. Specific monitoring ofthe transmission resources of the transmission link US by the resourcemanager RM is indicated by the dashed arrow in the FIGURE.

In addition, a terminal EG1 is connected to the Local Area Network LAN1and a terminal EG2 is connected to the Local Area Network LAN2. Theterminals EG1 and EG2 can be implemented as any communication terminals,e.g. for voice, video and/or data communication, or as a personalcomputer. Address information A1 is assigned to the terminal EG1 andaddress information A2 is assigned to the terminal EG2. The terminalsEG1 and EG2 can be unambiguously addressed and identified in thecommunication system via address information A1 and A2 respectively. Inan alternative embodiment, another router, switch or another networknode of the communication system can be provided instead of at least oneof the terminals EG1 and EG2, for example.

The communication system additionally has a central so-called gatekeeperGK which is linked to the resource manager RM. The gatekeeper GK isresponsible for logic control, i.e. for setting up and clearing down aswell as monitoring connections in the communication system. To set up aconnection with guaranteed Quality of Service, the origin anddestination of the connection to be set up must be communicated to thegatekeeper GK. In this embodiment, the gatekeeper GK satisfies ITU-TRecommendation H.323.

According to a further embodiment, a SIP server supporting a so-calledSession Initiation Protocol (SIP) compliant with the IETF Standard canbe used instead of the gatekeeper GK.

In the present embodiment, the setting-up of a connection V, e.g. forvoice transmission (VoIP: Voice over Internet Protocol), with guaranteedQuality of Service from the terminal EG1 to the terminal EG2 will beconsidered. As part of connection setup, connection setup signaling isperformed between the terminal EG1 and the gatekeeper GK and between thegatekeeper GK and the terminal EG2. For this purpose logical signalingchannels are set up between the terminal EG1 and the gatekeeper GK andbetween the gatekeeper GK and the terminal EG2 which are illustrated bysolid arrows in the FIGURE. Connection setup signaling is preferably inaccordance with ITU-T Recommendation H.323 v2. This type of connectionsetup signaling is also commonly known as “fast connect”.

As part of initiating connection setup, connection setup information VIis communicated to the gatekeeper GK by the terminal EG1. The connectionsetup information VI contains the address information A1 identifying theoriginating endpoint EG1, the address information A2 identifying thedestination endpoint EG2 as well as a resource request RA. Theconnection setup information VI is then communicated to the resourcemanager RM by the gatekeeper GK. For this embodiment it will be assumedthat a voice connection in accordance with ITU-T Recommendation G.711with a transmission bandwidth of 80 kbit/s is requested using theresource request RA.

According to an alternative form of connection setup, the connectionsetup information VI can contain a logical destination address (notshown), such as an alias address, e-mail address, URL (Uniform ResourceLocator) or E.164 address, identifying the destination endpoint EG2.This logical destination address is converted by the gatekeeper GK intoa transport address, in this case A2, identifying the destinationendpoint EG2 and is transmitted as such to the resource manager RM. Inthis context, the term “transport address” refers to address informationon the basis of which data packets can be routed through thecommunication system. A transport address of this kind can, for example,comprise an IP (Internet Protocol) address and a port number.

On the basis of communicated address information A1 and A2, the resourcemanager RM determines whether the connection V to be set up is to bedirected via the transmission link US. If the transmission resources ofa plurality of transmission links are to be administered by the resourcemanager RM, the resource manager RM determines via which of thesetransmission links the connection V is to be routed. This can preferablybe performed using a table (not shown) in which an originating anddestination address of a connection are assigned one or more individualtransmission links via which that connection is to be routed.

If it is established by the resource manager RM that the connection V tobe set up is routed via the transmission link US, the currentlyavailable transmission resources of that transmission link US aredetermined. This can be performed e.g. on the basis of another table(not shown) in which the currently available transmission resources—insome cases service- and/or priority-class-specific—for one or moreindividual transmission links of the communication system are listed.For the present embodiment it will be assumed that 50 kbit/s oftransmission bandwidth is still available for the transmission link US.The transmission bandwidth determined is then compared with the 80kbit/s transmission bandwidth required in the resource request RA.Provided that, as in this embodiment, the available bandwidth is foundto be less than the transmission bandwidth requested, resourceinformation RI is communicated to the gatekeeper GK by the resourcemanager RM. The resource information RI specifies the level of resourcesof the transmission link US currently still available. The gatekeeper GKthen generates a message M containing the resource information RI andcommunicates it to the originating endpoint, in this case the terminalEG1.

As a variant of this method, instead of the resource information RIconcerning the currently available bandwidth, a standardized specifiedbandwidth lower than or equal to the currently available transmissionbandwidth can be communicated with the message M. For example, aspecified bandwidth of 22 kbit/s for connections in accordance withITU-T Recommendation G.723 can be communicated with the message M.

According to another variant of the method, a specification for atransmission method to be used, having a bandwidth requirement less thanor equal to the currently available bandwidth, can be communicated withthe message M instead of the resource information RI. Thus, for example,a transmission method in accordance with ITU-T Recommendation G.723 orG.712 for the connection V can be specified by the message M.

According to another variant of the method, generation of the message Mcan also be dependent solely on whether or not the connection V to beset up is to be routed via the transmission link US; i.e. in particularirrespective of temporary variations in the transmission resources ofthe transmission link US. For example, whenever it is determined thatthe connection V is routed via the transmission link US, a message M canbe transmitted causing the transmission resources of the connection tobe set up to be limited to a specified fixed resource requirement.

The message M can also be transmitted by the gatekeeper GK to theterminal AG2 for similar purposes.

If limiting the transmission resources of the connection to be set up tothe still available level of resources of the transmission link USproves to be impractical, or if the remaining transmission resourcesstill available after connection setup were disadvantageously low, thetransmission resources of existing connections routed via thetransmission link US can also be reduced by appropriate messages.

The message M can preferably be transmitted in the form of a so-calledRAS (Registration, Admission and Status) message in accordance withITU-T Recommendation H.323. RAS messages of this type allow, among otherthings, the transmission bandwidth of connections to be varied.

The message M causes the terminal EG1 to establish the connection V witha resource requirement reduced in accordance with the resourceinformation RI. For this purpose, the terminal EG1 sends connectioninformation VI, containing the originating and destination addressinformation A1 and A2, and a reduced resource request RA2 to thegatekeeper GK. No more than the currently available transmissionresources (specified by the resource information RI) of the transmissionlink US is requested by the resource request RA2. If connection setupcannot be implemented using reduced transmission resources of this kind,connection setup is terminated. In this embodiment, transmissionresources for a connection as defined in Recommendation G.723 with atransmission bandwidth of 22 kbit/s are requested by the transmissionrequest RA2. The gatekeeper GK then causes the transmission resourcesrequested by the transmission request RA2 and still available to bereserved by the resource manager RM. By appropriate connection setupsignaling, the gatekeeper GK then initiates logical setup of theconnection V with the 22 kbit/s transmission bandwidth requested by thetransmission request RA2 between the terminals EG1 and EG2.

When the connection has been set up, user data can be exchanged betweenthe terminals EG1 and EG2 via the Local Area Networks LAN1 and LAN2 withguaranteed Quality of Service, i.e. in this case with a guaranteedtransmission bandwidth of 22 kbit/s.

The transmission resources of the transmission link US can in some casesbe administered and monitored by the resource manager RM on aservice-class-specific, priority-class-specific and/ortransmission-direction-specific basis.

A simple implementation of resource management of this kind relates toclassifying the data traffic into different service and/or priorityclasses and assigning each of these classes a portion of the availabletransmission resources of the transmission link US—possibly on atransmission-direction-specific basis. Such data traffic classes arealso commonly known as diffserv classes.

Information concerning specific transmission peculiarities of thetransmission link US, such as a high data loss rate (e.g. in the case ofradio links), high transmission delay and/or a particular type oftransmission cost billing, can be communicated with the message M.Depending on such information, a transmission method which is less proneto data loss or transmission delay can be selected by the terminal EG1.

The transmission bandwidth required by the connection V can be variedwithin specified limits by varying the time spacing of the data packetsto be transmitted in respect of the connection V. By lengthening thesetime spaces, the transmission bandwidth is reduced, as the portion ofthe control data transported in the header of the data packets becauseof the associated enlargement of the data packets is reduced in linewith the data transmission volume. However, this increases bothtransmission delay and proneness to data packet losses. Reducing thespacing of the data packets has the opposite effect in each case.

The invention has been described in detail with particular reference topreferred embodiments thereof and examples, but it will be understoodthat variations and modifications can be effected within the spirit andscope of the invention.

1. A method of setting up a connection with a guaranteed Quality ofService via a transmission bottleneck for a packet-orientedcommunication network, comprising: administering transmission resourceson the transmission bottleneck by a resource manager; transmittingconnection information identifying an origin and a destination of theconnection to the resource manager to set up a connection withguaranteed Quality of Service; reviewing the connection information atthe resource manager and determining whether the connection is to berouted via the transmission bottleneck; depending solely on whether theconnection is to be routed via the transmission bottleneck, generating amessage specifying a level of transmission resources of the transmissionbottleneck available currently; sending the message to the origin of theconnection; and requesting the level of the transmission resources forthe connection specified by the message, at the origin of theconnection, as a function of the message; wherein the requestedtransmission resources are limited to a reduced resource requirement ifthe connection is to be routed via the transmission bottleneck; andwherein the transmission bottleneck is a single transmission link. 2.The method according to claim 1, wherein the message is generated as afunction of available transmission resources on the transmissionbottleneck.
 3. The method according to claim 2, wherein an alreadyexisting connection is routed via the transmission bottleneck,transmission resources were assigned to the already existing connection,and the assignment of transmission resources are modified for thealready existing bottleneck according to whether the connection is to berouted via the transmission bottleneck.
 4. The method according to claim3, wherein a request for transmission resources is transmitted to theresource manager with the connection information, and the message isgenerated in accordance with the transmission resources requested. 5.The method according to claim 4, wherein the message includes resourceinformation corresponding to the available transmission resources on thetransmission bottleneck, and transmission resources for the connectionare selected in accordance with the resource information.
 6. The methodaccording to claim 5, wherein the message includes method informationconcerning a potential transmission method for the connection, and atransmission method for the connection is selected at the origin of theconnection based on the method information.
 7. The method according toclaim 6, wherein connection setup is based on whether the originsupports the selection of the transmission resources requested for theconnection.
 8. The method according to claim 7, wherein connection setupis based on to what extent the origin supports the selection of thetransmission resources requested for the connection.
 9. The methodaccording to claim 8, wherein the transmission resources of thetransmission bottleneck are administered by the resource manager on aservice- and/or priority-class-specific basis.
 10. The method accordingto claim 9, wherein a gatekeeper provides logical setup of theconnection.
 11. The method according to claim 1, wherein an alreadyexisting connection is routed via the transmission bottleneck,transmission resources were assigned to the already existing connection,and the assignment of transmission resources are modified for thealready existing bottleneck according to whether the connection is to berouted via the transmission bottleneck.
 12. The method according toclaim 1, wherein a request for transmission resources is transmitted tothe resource manager with the connection information, and the message isgenerated in accordance with the transmission resources requested. 13.The method according to claim 1, wherein the message includes resourceinformation corresponding to the available transmission resources on thetransmission bottleneck, and transmission resources for the connectionare selected in accordance with the resource information.
 14. The methodaccording to claim 1, wherein the message includes method informationconcerning a potential transmission method for the connection, and atransmission method for the connection is selected at the origin of theconnection based on the method information.
 15. The method according toclaim 1, wherein connection setup is based on whether the originsupports the selection of the transmission resources requested for theconnection.
 16. The method according to claim 1, wherein connectionsetup is based on to what extent the origin supports the selection ofthe transmission resources requested for the connection.
 17. The methodaccording to claim 1, wherein the connection information includesbottleneck information identifying a desired bottleneck for theconnection, and on the basis of the bottleneck information, it isdetermined whether the transmission bottleneck is the desiredbottleneck.
 18. The method according to claim 1, wherein thetransmission resources of the transmission bottleneck are administeredby the resource manager on a service- and/or priority-class-specificbasis.
 19. The method according to claim 1, wherein a gatekeeperprovides logical setup of the connection.